Mechanism for preventing excessive relative swinging of an articulated aerial device



Aug. 19, 1969 Filed Nov. 29, '1967 w. A. PRESCOTT ET AL MECHANISM'FOR PREVENTING EXCESSIVE RELATIVE SWINGING- OF AN ARTICULA-TED 'AERIAL' DEVICE 2 Sheets-Sheet; 2- 7 INVENTORS. William A. Prescoff Raymond J. Wachf Wayne R. Sfal/ard '7 E A'rramsvs United States Patent (1 3,461,989 MECHANISM FOR PREVENTING EXCESSIVE RELATIVE SWINGING OF AN ARTICULATED AERIAL DEVICE William A. Prescott, Grandview, Mo., and Raymond J. 'Wacht, Overland Park, and Wayne R. Stallard, Westwood Hills, Kans., assignors, by mesne assignments, to A. B. Chance Company, Centralia, Mo., a corporation of Missouri Filed Nov. 29, 1967, Ser. No. 686,524 Int. Cl. E06c /36 U.S. Cl. 182-19 Claims ABSTRACT OF THE DISCLOSURE Satety mechanism for an aerial lift prevents tipping by automatically limiting the extent to which the elevated operators station may be moved toward a position where a potentially dangerous situation might be presented. This is accomplished by use of a sensor located adjacent the zone of articulation between a pair of booms and operable in response to movement of linkage which pivotally interconnects the booms. The linkage used to move the booms generally has more movement than required to move the booms through their various positions, A sensor controls and limits the maximum movement of the booms. The effect of the sensor is to deactivate the power means which elevate the booms immediately upon the operators station reaching a preselected position well within the limits of adequate safety whether ascent or descent is accomplished by simultaneous operation of both booms or either of them and regardless of which boom is operated first.

It is the primary object of the present invention to eliminate the hazard of tipping which is normally inherent in aerial lift equipment, presenting a potentially dangerous condition insofar as death and injury are concerned, not only to operators being elevated, but to others working in the vicinity of such equipment.

The most important object of the instant invention is the provision of limiting mechanism which is not only out of the reach of the elevated operator, preventing him from tampering with the mechanism to render it ineffective in assuring his own safety, but to provide in the entire assembly an arrangement which requires corrective measures on the part of the operator whenever certain limits are reached before he is able to change his position in a direction which would be unfavorable from a safety standpoint.

Another important object of our present invention is to provide safety control mechanism that is entirely divorced from the operators support station, from the elements which couple such station with its boom, and from such boom itself to the end that there is no interference whatsoever with proper function as the result of necessary and normal movements of such components of the aerial equipment.

Still another important object of our instant invention is the provision of a safety control that requires a minimum amount of set-up time and effort and which may be set up, adjusted and maintained at ground level independent of the operators station and its supporting boom.

A further object of the present invention is to provide a safety control which is located in an area that is immediately adjacent the power means which it controls, i.e., the hydraulic piston and cylinder assemblies for actuating the booms, thereby reducing the number of potentially troublesome joints, fittings and other components 3,461,989 Patented Aug. 19, 1969 ice required for an operable connection of the control into the system.

A still further object of the instant invention is the provision of a safety control whose means of actuation is fixed within the basic design of the aerial lift equipment, rendering it, for the most part, tamper free.

In the drawings:

FIGURE 1 is a side elevational view of an articulated aerial device embodying mechanism for preventing excessive relative swinging of certain components of the lift apparatus in accordance with our present invention;

FIG. 2 is an enlarged, fragmentary, elevational view of the booms positioned as shown in FIG. 1, parts being broken away to reveal details of construction;

FIG. 3 is an enlarged, fragmentary, elevational view of the turret and the lower boom positioned as shown in FIG. 1, parts being broken away to reveal details of construction;

FIG. 4 is a view similar to FIG. 2, but showing the upper boom raised;

FIG. 5 is a view similar to FIG. 2, but showing both booms raised;

FIG. 6 is an enlarged, fragmentary, elevational view showing the bucket in its raised position;

FIG. 7 is an enlarged elevational view of the control unit showing that side thereof opposite to that seen in FIGS. 1, 2, 4 and 5;

FIG. 8 is an enlarged view showing that end of the control unit proximal to the pivot between the booms and illustrating the relationship thereto of the link which actuates the same; and

FIG. 9 is an enlarged plan view of the control unit, parts being broken away and in section for clearness.

FIG. 1 of the drawings illustrates a truck 10 having a turntable or turrent 12 rotatable thereon about an upright axis. Turret 12 carries lift apparatus 14 that includes a lower boom 16 and an upper boom 18, the latter having a workmans station, such as a bucket 20, suspended therefrom by a pintle 22. A first pivot means 24 mounts boom 16 on turret 12 for swinging movement toward and away from support 10 and a second pivot means 26 mounts boom 18 on boom 16 for swinging movement toward and away from boom 16.

A first power means in the nature of a double acting,

,. hydraulic piston and cylinder assembly 28 pivotally interconnects the boom 16 and turret 12 and serves to raise and lower the boom 16 relative to support 10. A second power means 30 of the same type as assembly 28, and pivotally connected with the boom 16, serves to raiseand lower the boom 18 relative to boom 16.

Linkage 32, pivotally connecting assembly 30 with booms 16 and 18, includes a first link 34 swingably connected to boom 18 and a second link 36 swingably connected to boom 16, the latter connection being in the nature of a pivot pin 38 on boom 16. Link 36 has a pair of integrally interconnected arms 40, each provided with a boss 42 as best seen in FIGS. -8 and 9.

An elongated rod-like member 44 has a pivotal connection 46 with a sensor unit 48, os-cillatable on pin 38, and a pivotal connection 50 with an arm 52 that is looped around pivot means 24 and attached to turret 12 at 53 (FIG. 3). Pivot connection 50 is held in a fixed spaced relationship to pivot means 24 as by use of a collar 55 rigid to arm 52 and surrounding the pivot means 24.

Unit 48 includes a body 54 which supports a pair of valves 56 and 58 having fluid ports 60 and spring-loaded plungers 62 and 64 respectively provided with rollers 66. Body 54 also supports spring-loaded rods 68 which carry anactuator yoke 70 for plungers 62 and 64. An inclined cam edge 72 along the bight of yoke 70 is engageable with rollers 66.

Valves 56 and 58 are, in the conventional manner, operably coupled in the hydraulic circuit for the cylinders of assemblies 28 and 30 such that when their plungers 62 and 64 are depressed by the yoke 70, as shown by full lines in FIG. 7, fluid may be directed to and from such cylinders to raise and lower the booms 16 and 18 in a normal manner. However, when the yoke 70 is shifted to the dotted line position of FIG. 7, against the actions of the springs for rods 68, the springs for plungers 62 and 64 force the latter outwardly to by-pass the fluid to the fluid receiver of the hydraulic circuit. Moreover, the plungers 62 and 64, when so released by the yoke 70, block the flow of fluid to one side of the cylinders such that the operator can, at that time, only reverse that one direction of travel of the booms 16 and 18. Noteworthy also, of course, is the fact that plungers 62 and 64 are so released only when the bosses 42 of arms 40 are against the ends of the legs of yoke 70 and the link 36 is swung to the position (relative to body 54) shown in FIGS. 4 and 5.

Assume, therefore, with truck 10 level as shown in FIG. 1, that an operator in bucket 20 actuates the manual control valve (not shown) which directs the hydraulic fluid under pressure from the pump of the hydraulic circuit to the assembly 30 such as to raise boom 18 about pivot 26 to the position shown in FIGS. 4 and 6. Upward swinging movement of boom '18 will be stopped automatically to prevent over-center movement of the bucket 20; i.e., as shown in FIG. 6, bucket 20 has not crossed over a vertical line through its pivot 22.

If a still higher position of bucket 20- is desired, the operator need merely raise the boom 16 slightly to depress plungers 62 and 64, thereby permitting the activation of assembly 28. When boom 16 reaches the position shown in FIG. 5, the boom 18 may be swung to an even greater angle with respect to boom 16 before the assemblies 28 and 30 are deactivated to preclude the bucket 20 from moving beyond the position shown in FIG. 6.

A maximum angle of safety between booms 16 and 18 (when boom 16 is positioned as shown in FIG. 4) should be preselected, and found that approximately 70 is quite satisfactory under most conditions that are expected to be encountered. However, such angle may be and is progressively increased, as above explained, as the boom 16 is raised, without bucket 20 moving past center. For example, if the boom 16 is substantially vertical as shown in FIG. (normally its limit should be fixed to short of vertical as shown, by limiting the stroke of its assembly 28) the angle between booms 16 and 18 may be increased to about 160. On the other hand, and conversely, as the boom 16 is lowered, such angle must be decreased from 160 to 70 as the boom 16 again approaches horizontal as shown in FIG. 4.

The 70 safety factor is maintained, without any movement of the body 54 on pin 38, when only the boom 18 is raised and lowered relative to boom 16. But when the position of boom 16 is changed from that shown in FIG. 4, the automatic and unique function of the rod 44 becomes important. It is but necessary to compare FIGS. 4 and 5 to note the way in which rod 44 rotates the body 54 clockwise about pin 38 as boom 16 moves from the position shown in FIG. 4 to the position of body 54 shown in FIG. 5, and conversely as boom 16 is lowered.

Thus, as assembly 28 alone is activated, the ends of the legs of yoke 70 move away from bosses 42 during ascent of boom 16, permitting the operator to, at the same time or later, increase the 70 angle between booms 16 and 18 to a 160 maximum; and move toward such ends of the legs of yoke 70 during descent of boom '16, forcing the operator to, .gradually or beforehand, decrease the angle between booms 16 and 18 from 160 to 70 by the time boom 16 is returned to horizontal.

Therefore, the four point linkage cannot be a parallelogram arrangement which would preclude rotation of body 54 about pin 38 during movement of boom 16. Instead,

the location of the four pivot points 24, 38, 46 and 50 (connecting the linkage 16 and 44 to turret 12 and to the body 54) with respect to each other governs the rotation of body 54 about pin 38 during movement of boom 16, arm 52 being employed merely to clear pin 24 in order to in effect attach rod 44 to turret 12 at pivot 50.

As long as bucket 20 is not permitted to swing too close to over-center the 70 angle selection as above suggested is not critical; limited over-travel does not present a dangerous situation. Thus, as is apparent in FIG. 7, for example, continued boom movement by inertia does not damage the control unit because yoke 70, travelling in a direction substantially at right angles to plungers 62 and 64, merely moves beyond rollers 66 after deactivation of assemblies 28 and 30.

It follows from the foregoing that there has been provided in aerial lift equipment, the combination of the outer boom 18, actuated by the linkage 32, with a fourbar mechanism (boom 16, rod 44 and pivots 24, 38, 46, 50) coupled with and sensitive to the articulation of the boom 16. The hydraulic control devices 56 and 58 are positioned by the four-bar mechanism in such manner as to be actuated when the yoke 70 is contacted by the bosses 42 on the arms 40 of the follower link 36 which, in turn, raises and lowers the boom 18. Such mechanism causes the spool-type valve devices 56 and 58 to locate in a proper angular relationship to the angular displacement of link 36 during movement of boom 18, it being kept in mind that although such displacement is different in amount from that of the boom 18, it is directly related thereto.

Important also is the fact that the devices 56 and 58 will not only limit the operation of the boom 16 during descent of the latter when boom 18 is in an unfavorable position, but will also limit the operation of boom 18 during ascent of the latter when boom 18 is in such unfavorable position. The position of the boom 18 relative to true vertical is limited regardless of the position of the boom 16. Not to be overlooked addtionally is the feature of the run-by means of yoke 70 beyond rollers 66 to allow for excessive travel of link 36 and to simplify initial set-up.

Again it is to be emphasized that there is no critical angle to be maintained between the booms nor is it important that the booms be limited to any certain elevated position short of vertical. Those factors depend on such things as the tipping moment of truck 10, the contemplated maximum weight which bucket 20 will be required to support during normal use, the length of the booms, etc. All such factors have been considered, however, in the 70 angle above mentioned. Moreover, such angular limit also keeps in mind that the attitude of truck 10 may not always be as shown in FIG. 1. A substantial down-hill slope of truck 10 fore and aft and/or laterally will not create a dangerous problem if the high margin of safety above suggested is maintained. It is important to appreciate that the objects herein initially set down are fully attained by the structure shown and described.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. In an aerial lift having a boom provided with means supporting the same for movement along a predetermined path of travel, power means connected with said boom for moving the same, and a coupling between said power means and the boom, mechanism sensitive to movement of said coupling for limiting the extent of said travel of the boom in one direction, said mechanism including:

a control for said power means adapted for operable connection with the latter,

said control having structure shiftable to and from a position deactivating said power means; and means disposing said structure within the path of movement of the coupling for engagement by the latter whereby said coupling shifts the structure to said position after the boom has travelled to said extent in said one direction.

2. The invention of claim 1,

said structure including a shiftable element controlling the power means, and

an actuator for said element,

said actuator being engaged by the coupling, and

having an over-travel in excess of that needed for full operation of said element, effective during continued movement of the boom, by virtue of inertia, beyond said extent of travel after deactivation of the power means.

3. The invention of claim 2,

said element and said actuator being reciprocable along relatively normal paths of travel.

4. In an aerial lift having a support, lift apparatus including a lower boom and an upper boom, a first pivot means mounting the lower boom on the support for up and down swinging movement, a first power means interconnecting the support and the lower boom for raising the lower boom, a second pivot means mounting the upper boom on the lower boom for up and down swinging movement, a coupling between the booms, and a second power means interconnecting the lower boom and said coupling for raising the upper boom, mechanism sensitive to movement of said coupling for limiting the position of the upper boom with respect to vertical regardless of the position of the lower boom, said mechanism including:

a sensor unit adjacent said coupling provided with a pair of controls each adapted for operable connection with a corresponding power means,

each control having structure shiftable to and from a position deactivating its power means;

mounting means attaching said unit to said apparatus for movement relative to the latter and disposed to place said structures within the path of travel of the coupling whereby the latter shifts said structures to said positions when engaged by the coupling; and

a connection between the support and said unit relsponsive to swinging of the lower boom for moving the unit relative to said apparatus and thereby varying the position of said structures relative to the coupling as the lower boom is swung.

5. The invention of claim 4,

said mounting means for said unit being on the lower boom.

6. The invention of claim 4,

said connection comprising an elongated member having a first pivotal connection with said support in spaced proximity to said first pivot means and a second pivotal connection with said unit in spaced proximity to said mounting means for said unit.

7. The invention of claim 6,

said coupling comprising a first link swingably connected to the upper boom and a second link swingably connected to the lower boom, with both links pivotally connected to said second power means,

said unit and said second link having a common swinging connection to the lower boom,

said structures being within the path of travel of the second link.

8. In an aerial lift having a support, lift apparatus including a lower boom and an upper boom, a first pivot means mounting the lower boom on the support for up and down swinging movement, a first power means interconnecting the support and the lower boom for raising the lower boom, a second pivot means mounting the upper boom on the lower boom for swinging movement toward and away from the lower boom, linkage pivotally interconnecting the booms, a second power means interconnecting the lower boom and said linkage for raising the upper boom away from the lower boom, a workmans station swingable suspended from the upper boom, mechanism sensitive to movement of said linkage for precluding over-center movement of said station relative to the upper boom throughout all positions of the booms within their respective paths of travel, said mechanism including:

a sensor unit adjacent said linkage provided with a pair of controls each adapted for operable connection with a corresponding power means,

each control having structure shiftable to and from a position deactivating its power means;

said linkage comprising a first link swingably connected to the upper boom and a second link swingable connected to the lower boom, with both links pivotally connected to said second power means,

said unit and said second link having a common swinging connection to the lower boom,

said structures being within the path of travel of the second link whereby the latter shifts said structures to said positions when engaged by the second link;

a connection between the support and said unit responsive to swinging of the lower boom for moving the unit relative to the lower boom and thereby varying the position of said structures relative to the second link as the lower boom is swung,

each structure including a shiftable element controlling its corresponding power means, and

an actuator for said elements,

the actuator being engaged by the second link.

9. The invention of claim 8,

each power means comprising a fluid operated piston and cylinder assembly,

each structure having a valve coupled with the corresponding assembly,

each element comprising a fluid control plunger for each valve respectively.

10. The invention of claim 9,

said plungers being yieldably biased away from positions permitting flow of fluid to their assemblies,

said actuator being yieldably biased toward a position holding the elements in said positions permitting flow of fluid to their assemblies.

References Cited UNITED STATES PATENTS 2,529,193 11/1950 Rueter 182-19 2,936,847 5/ 1960 Eitel 182-19 3,141,562 7/1964 McAdams 2l2--39 3,035,712 5/ 1962 Nowack 18219 3,204,720 9/1965 Eitel 182l9 3,371,799 5/1968 Brownell 21239 3,371,800 5/1968 Grove 212-39 REINALDO P. MACHADO, Primary Examiner U.S. Cl. X.R. 

